A blind riveter (see U.S. Pat. No. 2,396,001) typically comprises a housing provided with a chuck that grips the mandrel of the blind rivet and with means for pulling this chuck back away from an orifice on the housing so as to retract the mandrel in the rivet and thereby upset the rivet end. The chuck is usually of the automatic one-way gripping type and is urged by a spring to a rest position normally adjacent the orifice.
The actuator for this chuck can be pneumatically powered. In order to obtain the necessary force a large-diameter piston is used which is provided with an endpiece that in some pneumatically powered riveters is directly connected with a wedge slidable along rollers. To both sides of this wedge there is provided an arm pivoted on the housing and these arms are connected at the forward section with a transverse rod on which a roller is mounted. The roller lies on the inclined side of the wedge and the front ends of the arms are engaged in recesses in a puller body connected to the chuck. This chuck in the corresponding portion of the housing lies at a right angle to the rest of the housing so that when the actuation wedge is displaced forwardly by the piston the roller engaging the wedge is moved upwardly to lever up the chuck.
The disadvantage of this system is that it is necessary that the relatively complicated actuation device be made to very exact tolerances in order to function properly, thereby making the pneumatic rivet setter a very expensive tool. In addition the device is relatively bulky and hard to use. Therefore the operator tires readily and must often assume an uncomfortable position in order to position the riveter properly over the workpiece.
Another type of device is known which uses a plurality of pneumatic cylinders. The common piston rod for the several pistons is connected directly to the pulling chuck so that the relatively lengthy assembly can be positioned in line with the mandrel at a right angle to the workpiece. Such a position is not only uncomfortable but is often impossible so that such devices have not met with widespread acceptance. In addition the use of several pistons often means that the reset time for the tool is relatively long, as the conventional reset spring is only slowly effective to drive the air out of the compartments in back of all of the pistons.